Method and system architecture for a self organizing network

ABSTRACT

A method and system architecture for a self-organizing network (SON) includes a first cell having a first user equipment classifier for determining one of cell edge and cell central. The SON also includes a second cell having a second user equipment classifier for determining one of cell edge and cell central. The system architecture and method provide a first transmit time interval (TTI) schema for user equipment within the area of coverage associated with the first cell and a TTI schema for user equipment within the area of coverage associated with the second cell, the second TTI schema differing from the first TTI schema. The user equipment is classified as cell centre or cell edge in dependence upon at least one of QoS requirement, geometry, periodic PSMM and CQI reports. The TTI schemas are used for “cell edge” user equipment by the respective cells.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/092,140, filed Apr. 21, 2011, which application in turn claimsbenefit of priority from U.S. Provisional Application No. 61/326,411,filed Apr. 21, 2010, which are hereby incorporated by reference in theirentirety as if fully set forth.

FIELD OF INVENTION

The present invention relates to methods and system architectures forSelf Organizing Network (SON) and is particularly concerned withwireless network performance that is subject to intercell interference.

BACKGROUND OF THE INVENTION

This section is not to be construed as reflecting an admission that anycontent herein is relevant prior art. Moreover, this section is not anindication of a search for relevant disclosures. All statements arebased on available information and are not an admission as to theiraccuracy or correctness.

The explosive adoption of video-enabled wireless mobile devices hascaused an explosion of data traffic and exposed the capacity constraintsof conventional wireless network topology.

Conventional wireless network (e.g. cellular network) deploymentrequires careful planning to maximize frequency reuse, minimize coveragedead zones and minimize inter-cell interference etc. The deployment islabour intensive due to significant amount of measurements and fieldtrials. To reduce the cost of deployment, many network operators deploymacro cells which provide larger coverage footprint and higher capacity.This approach works when the subscribers' service types are mainlyconversational (i.e. voice), interactive (e.g. web browsing, instantmessaging etc.) or low rate streaming, These are the typical servicetypes for 2G (e.g. GSM) and early 3G (e,g. UMTS Release 99 and CDMA2000)cellular networks where macro cell provides adequate quality of serviceto fulfill majority subscriber's needs.

More subscribers demand for faster data service as the bit rate at theair interface increases with the advance of the wireless technology(i.e. 3.5G and 4G). One instance of 3.5G is HSPA. One example of 4Gnetworks is LTE (3GPP Release 8 and beyond), another is WiMax(IEEE802.16e and beyond). Given the limited available spectrum, thecapacity becomes a serious issue for conventional macro cell. Thecapacity issue has caused a shift in cellular network deploymentparadigm from well partitioned large coverage macro cells to denselydeployed smaller cells (e.g. picocell and ferntocell), many being addeddynamically in non-fixed locations.

Today's SON (i.e. self configuration and provision) are not sufficientfor densely deployed small cells to operate properly. SON capable ofcoordinating among neighboring cells on radio resource allocation isessential for densely deployed small cells to operate properly.

SUMMARY OF THE INVENTION

The present invention provides system architecture for a Self-organizingNetwork (SON) using Fractional Time Reuse (FTR) that can be applied, butnot limited to, 3G/4G wireless cellular networks and beyond, as well asother wireless network.

In accordance with an aspect of the present invention there is provideda FTR SON system for optimizing the network performance (e.g. capacity,throughput, quality of service) by coordinating network elements ingroups.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further understood from the followingdetailed description with reference to the drawings in which:

FIG. 1 illustrates Fractional Time Reuse (FTR) SON for Two-Cell Case;

FIG. 2 illustrates FTR SON for Three-Cell Case; FIG. 3 illustrates FTRSON for Three-Cell Covering the Entire Layer of Network;

FIG. 4 illustrates FTR SON for Multi-Layer Network, e.g., Pico-cells inMulti-floor Office Building;

FIG. 5 illustrates Network Procedures for FTR;

FIG. 6 illustrates UE procedures for FTR; and

FIG. 7 illustrates NoteB procedures for FTR.

DETAILED DESCRIPTION OF MODES OF PRACTICING THE DISCLOSURE

Referring to FIG. 1 there is illustrated a fractional time reuseself-organizing network (FTR SON) operating in two-cell configurationthat uses embodiments of the present invention. The FTR SON 100 includesa first cell 102 and a second cell 104, which have an overlapping region106. The first cell 102 includes a first node 108 (NodeB₀) and a userequipment 110 (UE₀) in the overlapping area 106. The first node 108 usesa first fractional time reuse schema 112 to connect to the user element110 (UE₀) when it is in the overlapping area 106. The second cell 104includes a second node 114 (NodeB₁) and a user equipment 116 (UE₁) inthe overlapping area 106. The second node 114 uses a second fractionaltime reuse schema 118 to connect to the user element 116 (UE₁) in theoverlapping area 106.

In operation, assuming NBi is the serving Downlink Shared Channel (DSCH)NodeB for UEi, i=0,1; where DSCH can be HS-DSCH for High Speed PacketAccess (HSPA) or Physical Downlink Shared Channel (PDSCH) for Long TermEvolution (LTE), The FTR SON 100 puts long term scheduling restrictionsonto the NodeB MAC scheduler such that the scheduling Time Transmissionintervals (TTIs) (2 ms for HSPA, 1 ms for LTE) for UEs at the edge ofthe cells are staggered, e.g., in the two-cells case shown, UE₀ 110 isserved on even numbering TTIs while UE₁ 116 is served on odd numberingTTIs. There is no restriction on the scheduling TTI timing for UEs 120and 122 in the center of cells 102 and 104 respectively.

In the FTR SON 100, UEs can be classified as Center UEs, e.g. UE 120 andUE 122 or Edge UEs, e.g. UE 110 and UE 116 via PDP context Quality ofService (QoS) requirement, Geometry ({circumflex over (1)}_(or)/I_(oc)),Channel Quality Indicator (CQI), Pilot Strength Meassuremnt Message(PSMM, Pilot Ec/Io), or similar SINR measurements performed at the UEsand reported to the NodeBs 108 and 114.

In a typical HSPA deployment, at least 50% NodeB power is allocated toHS-PDSCHs, staggering scheduling TTIs can significantly reduce Ioc,therefore improve cell edge UEs performance. Similar performanceimprovement can be expected for LTE.

Referring to FIG. 2 there is illustrated FTR SON for three-cell case.This is the generalization of the two-cell case in FIG. 1, which issignificant since the entire network layer can be covered by groupingcells in groups of three. The three-cell FTR SON 200 includes cells 202,204 and 206. Each cell 202, 204 and 206 has a respective NodeB, NB₀ 210,NB₁ 212 and NB₂ 214 in communication with a respective user equipmentUE, UE₀ 220, UE₁ 222 and UE₂ 224.

In operation, in the example shown in FIG. 2, each NB₁ is the servingDownlink Shared Channel (DSCH) NodeB for UE_(i), i=0,1,2. UE₀ 220 isinterfered by NB₁ 212 and NB₂ 214, UE₁ 222 is interfered by NB₂ 214, UE₂224 is interfered by NB₀ 210. The FTR SON 200 puts a long termscheduling constrain onto NodeB MAC scheduler such that each UE_(i) inservice overlap areas 230, 232 and 234, is scheduled on TTIs numbered as3n+i, respectively, i=0, 1, 2, shown as 240, 242 and 244 respectively.

By staggering the Transmission Time Interval (TTI) for UE₀, UE₁, UE₂intercell interference can be reduced considerably.

Referring to FIG. 3 there is illustrated the 3-cell grouping forcovering an entire network layer with significantly reduced intercellinterference at cell boundary. In the network 300, each cell 310 isdivided into three sectors 320, 321 and 322, corresponding to I=0, 1, 2as used in FIG. 2. Through this arrangement of Transmission TimeIntervals (TTI) neighboring cells 310′ and 310″ each use a different TTIfrom their adjacent neighbor.

Referring to FIG. 4 there is illustrated FTR SON for a multi-layernetwork. The FTR SON 400 of FIG. 4, can be used, for example forpico-cells in a multi-floor office building. The example FTR SON 400shown includes four cells, 410, 420, 430 and 440 in two layers 450 and460. Hence, the FTR SON 400 is in the form of 4n, 4n+1, 4n+2, and 4n+3can be applied. In general, an FTR SON in the form of M*n, . . . ,M*n+(M−1), where M in the Fractional Time Reuse Factor, is used when Mcells are grouped together for optimization.

Referring to FIG. 5 there is illustrated network procedures for a FTRSON. The process of NodeB registration 500 begins with determining thetopology of the neighbor group 510. The number of cells in the groupdetermines the Fractional Time Reuse Fractor, M 520 and the NodeB timeslot assignment M*n, . . . , M*n+(M−1) 530.

Referring to FIG. 6 there is illustrated UE procedures for an embodimentof FTR SON. Each UE periodically reports a Pilot Strength MeasurementMessage (PSMM) to determine a DSCH serving cell 600. Once the servingcell is determined, UE periodically reports 610 CQI to assist NodeB todetermine UE's location (i.e, cell center vs cell edge).

Referring to FIG. 7 there is illustrated NodeB procedures for anembodiment of FTR SON. Each NodeB receives 700 a QoS requirement when aPDP context is configured/reconfigured for each individual UE and 710 aPSMM report from each individual UE via accessing 720 PSMM report fromRRC API to determine DSCH serving cell per T-add network optimizationparameter. After serving cell determination, NodeB receiving CQI reportfrom individual UE via accessing 730 CQI report from MAC API. NodeB cancompute the averaged CQI over a configurable time interval incombination of QoS requirement to determine each UE's location 740(i.e., cell center vs cell edge). Finally, scheduling constrains to MACscheduler is posted 750 via MAC API: unrestricted scheduling for UEsbelonging to cell center category while restricted scheduling (FTR withspecific time slot) for UEs belong to cell edge category.

Having now fully described the inventive subject matter, it will beappreciated by those skilled in the art that the same can be performedwithin a wide range of equivalent modifications, variations andadaptations without departing from the scope patent disclosure.

While this disclosure has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications. This application is intended to cover any variations,uses, or adaptations of the disclosure following, in general, theprinciples of the disclosure and including such departures from thepresent disclosure as come within known or customary practice within theart to which the disclosure pertains and as may be applied to theessential features hereinbefore set forth.

1. A method of configuring a self organizing wireless network (SON), themethod comprising: receiving a Quality of Service (QoS) requirement foreach individual user equipment (UE) served by a wireless node of acellular network; receiving a pilot signal strength measurement (PSMM)from each UE; determining downlink shared channel (DSCH) servingwireless node for each UE; receiving channel quality indicator (CQI) foreach UE; computing average CQI value per each UE over a defined timeinterval in combination with QoS requirements to determine each UEsservice category; determining individual each UE's service category fromthe determined service category; and posting scheduling constraints forthe wireless nodes of the cellular network to medium access control(MAC).
 2. The method of claim 1 wherein the scheduling constraintscomprise posting unrestricted scheduling for UEs having a servicecategory belonging to cell center category and restricted scheduling forUEs having a service category belonging to cell edge category.
 3. Themethod of claim 1 wherein the QoS requirement is received when a radiobearer context is configured or reconfigured.
 4. The method of claim 1wherein posting scheduling the constraints comprises: assigning a firsttransmit time interval to a first wireless node; assigning a secondtransmit time interval to a second wireless node different from thefirst transmit time interval; and the first wireless node using thefirst transmit time interval for UE for mitigating interference from thesecond wireless node.
 5. The method of claim 4 wherein the using thefirst transmit time interval is for UE in a service coverage areaoverlapping with the second wireless node.
 6. The method of claim 4wherein using the first transmit time interval is for UE in a portion ofits service coverage area adjacent to the second wireless node.
 7. Themethod of claim 4 wherein the first and second transmit time intervalsare assigned in dependence upon a fractional time reuse factor and nodenumber.
 8. The method of claim 7 wherein the transmit time intervals areassigned based upon a formula M×n+i, where M is the fractional timereuse factor and n is the node number and i is a random number rangedfrom 0 to M−1.
 9. The method of claim 4 wherein determining the UEservice category is in dependence upon at least one of QoS requirement,geometry, periodic PSMM and CQI reports.
 10. The method of claim 9wherein the step of using the first transmit time interval is only foruser equipment classified as cell edge.
 11. The method of claim 1wherein posting scheduling constraints comprises: determining afractional time reuse (FTR) factor based on a number of wireless nodeshaving an overlapping coverage area; determining long-term schedulingrestrictions based on the FTR factor for scheduling transmission timeintervals (TTIs) of each of the wireless nodes, the long-term schedulingassigning a unique subset of TTIs to each of the wireless nodes so thattransmissions according to different long term scheduling restrictionsare staggered in time; and assigning each of the determined long-termscheduling restrictions to a respective one of the wireless nodes foruse in scheduling transmission times of user equipments (UEs) served bythe wireless nodes on any of the transmission frequencies used by thewireless nodes; wherein the long-term scheduling restrictions of thewireless nodes are enforced for UEs classified to be at an edge of awireless node's coverage area; and wherein the long-term schedulingrestrictions of the wireless nodes are not enforced for UEs classifiedto be at a center of a wireless node's coverage area.
 12. The method ofclaim 11, wherein each of wireless nodes are grouped together based onthe overlapping coverage area are identified by respective positiveintegers.
 13. The method of claim 11, wherein the FTR factor is equal tothe number of wireless nodes having the overlapping coverage area. 14.The method of claim 13, wherein each of the long-term schedulingrestrictions schedules a TTI according to:TTI _(ni) =Mn+i where: M is the FTR factor; TTI_(ni) is the n^(th) TTIfor an i^(th) wireless node; and i is an integer identifying thewireless node.
 15. The method of claim 13, determining individual eachUE's service category as one of: a cell center UE; and a cell edge UE.16. The method of claim 15, wherein the classifying the UE is based uponat least one of QoS requirement, geometry, periodic PSMM and CQIreports.
 17. The method of claim 11, wherein each TTI is approximately 1ms to 2 ms in length.
 18. A non-transitory computer readable memorycontaining instructions for configuring a self organizing wirelessnetwork (SON), the instructions which when executed by a processor forperforming: receiving a Quality of Service (QoS) requirement for eachindividual user equipment (UE) served by a wireless node of a cellularnetwork; receiving a pilot signal strength measurement (PSMM) from eachUE; determining downlink shared channel (DSCH) serving wireless node foreach UE; receiving channel quality indicator (CQI) for each UE;computing average CQI value per each UE over a defined time interval incombination with QoS requirements to determine each UEs servicecategory; determining individual each UE's service category from thedetermined service category; and posting scheduling constraints for thewireless nodes of the cellular network to medium access control (MAC).19. A system for configuring a self organizing wireless network (SON)comprising: a component for receiving a Quality of Service (QoS)requirement for each individual user equipment (UE) served by a wirelessnode of a cellular network; a component for receiving a pilot signalstrength measurement (PSMM) from each UE; a component for determiningdownlink shared channel (DSCH) serving wireless node for each UE; acomponent for receiving channel quality indicator (CQI) for each UE; acomponent for computing average CQI value per each UE over a definedtime interval in combination with QoS requirements to determine each UEsservice category; a component for determining individual each UE'sservice category from the determined service category; and a componentfor posting scheduling constraints for the wireless nodes of thecellular network to medium access control (MAC).